Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.73	7.580%	$111.5927	$111.59	$111.60	$111.60
Purchase #2	$144.60	6.298%	$153.7069	$153.71	$153.70	$153.70
Purchase #3	$186.26	5.294%	$196.1206	$196.12	$196.10	$196.10
Purchase #4	$244.75	3.786%	$254.0162	$254.02	$254.00	$254.00
Purchase #5	$139.57	5.771%	$147.6246	$147.62	$147.60	$147.60
Purchase #6	$183.83	11.534%	$205.033	$205.03	$205.05	$205.00
Purchase #7	$212.37	4.657%	$222.2601	$222.26	$222.25	$222.30
7 purchase totals =	$1,215.11		$1,290.3541	$1,290.35	$1,290.30	$1,290.30